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The Longitudinal Spin Program at PHENIX

Dive into the longitudinal spin program at PHENIX, highlighting measurements, data insights, and future challenges in understanding the proton's spin structure. Discover rare probes experiments, helicity asymmetries, and luminosity and polarization studies.

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The Longitudinal Spin Program at PHENIX

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  1. The Longitudinal Spin Program at PHENIX Joe Seele for the PHENIX Collaboration (University of Colorado at Boulder) RHIC User’s Meeting - May 27, 2008

  2. Outline • Introduction to Spin Puzzle and p+p • Measurements at PHENIX • ALLs at 200 GeV and 62.4 GeV • What have we learned from PHENIX data? • PHENIX at 500 GeV … time permitting J. Seele - RHIC User's Meeting - 5/27/2008

  3. The Proton Spin Puzzle A future challenge Beginning to be measured at RHIC (and hopefully EIC) The proton is viewed as being a “bag” of bound quarks and gluons interacting via QCD Spins + orbital angular momentum need to give the observed spin 1/2 of proton Fairly well measured only ~30% of spin J. Seele - RHIC User's Meeting - 5/27/2008

  4. ΔG in Polarized p+p Collisions … + + + The LO result for aLL is nonzero for all subprocesses J. Seele - RHIC User's Meeting - 5/27/2008

  5. PHENIX A rare probes experiment Central Arms: • γ/π0/η detection • Electromagnetic Calorimeter (-0.35 < η < 0.35) • PC3 - Charge Veto • Charged Particle Detection/ID • DC • RICH (pion ID pT > 4.7 GeV/C) Global Detectors: • Relative Luminosity • Beam-Beam Counter (BBC) (+- 3.1 < η < 4.0) • Zero-Degree Calorimeter (ZDC) (+- 6.9 < η < infinity) • Local Polarimetry - ZDC J. Seele - RHIC User's Meeting - 5/27/2008

  6. Measuring Helicity Asymmetries <PT/P>=10±2(%) <PL/P> =99.48±0.12±0.02(%) PHENIX Central Arms+ PHENIX Muon Arms What to measure : N’s - Final state (π,η,γ,”jet”, J/Ψ) P’s - Polarization at IR R - Relative Luminosity PHENIX ZDCs+HJet+CNI PHENIX ZDCs+BBCs Local Polarimetry Relative Luminosity run5 values <PT/P>=14±2(%) <PL/P>=98.94±0.21±0.04(%) J. Seele - RHIC User's Meeting - 5/27/2008

  7. Luminosity and Polarization J. Seele - RHIC User's Meeting - 5/27/2008

  8. π0 ALL at 200 GeV PRD 73,091102/PRL 93,202002/PRD 76,051106 • Large branching ratio to diphoton • Produced in large quantities • Strong correlation to gluons in initial state -> See subprocess fractions • run5/run6 results included in recent DSSV fit PRD 76,051106 PRL 91,241803 J. Seele - RHIC User's Meeting - 5/27/2008

  9. π0 ALL at 62.4 GeV 200 GeV 62.4 GeV • Same effects as 200 GeV π0 • Needs NLL for agreement • Probes a different range in xb arxiv:0801.4555 J. Seele - RHIC User's Meeting - 5/27/2008

  10. η ALL at 200 GeV • Produced ~1/2 as much as π0 • 40% diphoton branching ratio • Different wavefunction from π0 • Stronger correlation to gluon/strange • Will be important at 500 GeV -> photon merging at higher pT Run3 PRC 75,024909 J. Seele - RHIC User's Meeting - 5/27/2008

  11. π+/π- ALL at 200 GeV • Produced in large quantities • No trigger at PHENIX • Cross section being calculated for these pTs • FFs should pick out different flavor mixtures -> good for consistency J. Seele - RHIC User's Meeting - 5/27/2008

  12. Cone ALL at 200 GeV • Similar to a jet measurement -> uses cone algorithm • Produced copiously, but no jet trigger at PHENIX • Theory is “corrected” to be more representative the cone sampling. • Not statistically separate from π and η measurements J. Seele - RHIC User's Meeting - 5/27/2008

  13. Direct Photons Run5 • Sensitive to sign and magnitude of delta-G • No FF convolution • A rare probe - lacks statistical power Run3 PRL 98,012002 J. Seele - RHIC User's Meeting - 5/27/2008

  14. Constraint from Measurements A series of constrained fits were done by Vogelsang and Stratmann in the GRSV model. They constrained the integral of ΔG at the input scale. Time to incorporate all measurements into the global fits J. Seele - RHIC User's Meeting - 5/27/2008

  15. Advertisement for other Long. Run-5 • Spin correlated transverse momentum (OAM) may contribute to jet kT (Meng Ta-chung et al., Phys. Rev. D40, 1989) • Calculate helicity asymmetry of kT in di-hadron correlations • J/Ψ production connected to heavy flavor production J. Seele - RHIC User's Meeting - 5/27/2008

  16. xb Coverage for Different Energies Coverage for sqrt(s) = 500 GeV Coverage for sqrt(s) = 200 GeV Coverage for sqrt(s) = 62.4 GeV J. Seele - RHIC User's Meeting - 5/27/2008

  17. 500 GeV Program and W Physics W’s decay then measure e,μ J. Seele - RHIC User's Meeting - 5/27/2008

  18. Forward Muons at PHENIX RPC2 RPC1(a,b) RPC2 RPC3 RPC3 J. Seele - RHIC User's Meeting - 5/27/2008

  19. Conclusions • PHENIX ALL measurements are pushing forward along many fronts • Measurements are luminosity hungry! • Need to put the current measurements into a global fit -> Daniel’s Talk Next • Stay tuned for PHENIX Transverse Spin Results -> Han’s Talk J. Seele - RHIC User's Meeting - 5/27/2008

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